These findings demonstrate that excess SFAs cause intracellular crystallization and subsequent lysosomal dysfunction, leading to the activation of the NLRP3 inflammasome, and provide novel insights into the pathogenesis of metabolic diseases.

The photoactivated adenylate cyclase (PAC) from the photosynthetic cyanobacterium Oscillatoria acuminata (OaPAC) detects light through a flavin chromophore within the N-terminal BLUF domain. BLUF domains have been found in a number of different light-activated proteins, but with different relative orientations. The two BLUF domains of OaPAC are found in close contact with each other, forming a coiled coil at their interface. Crystallization does not impede the activity switching of the enzyme, but flash cooling the crystals to cryogenic temperatures prevents the signature spectral changes that occur on photoactivation/deactivation. High-resolution crystallographic analysis of OaPAC in the fully activated state has been achieved by cryocooling the crystals immediately after light exposure. Comparison of the isomorphous light-and dark-state structures shows that the active site undergoes minimal changes, yet enzyme activity may increase up to 50-fold, depending on conditions. The OaPAC models will assist the development of simple, direct means to raise the cyclic AMP levels of living cells by light, and other tools for optogenetics.cAMP | BLUF domain | optogenetics | photoactivation | allostery

An adamantane-linked tetracene dyad (Tc-Ad-Tc) undergoes exergonic intramolecular singlet fission (SF), producing longlived (t = 175 µs) and high-energy (2 ´ 1.03 eV) multiexciton. Time-resolved absorption, fluorescence decay, and electron paramagnetic resonance (EPR) spectroscopic analysis revealed that the long-lived triplet species is generated in this system via correlated triplet pair having singlet and quintet characteristics. Time-resolved EPR analysis revealed formation of syn-and anti-conformers in the quintet, i.e. 5 ( 3 Tc-Ad-3 Tc)*. The quintet generation requires small conformational motion to induce singlet-quintet spin relaxation. The presence of aliphatic linkages, like the rigid adamantane group, may enable effective conservation of intrinsic high S1 and T1 levels of the original monomers, moderate bridge-mediated s-p interaction leading to exergonic intramolecular SF involving 1 Tc*-Ad-Tc ® 1 ( 3 Tc-Ad-3 Tc)*, and prevention of undesirable triplet-triplet annihilation, finally result in long-lived and high-energy multiexciton.

As altering permanent shapes without loss of material function is of practical importance for material molding, especially for elastic materials,s hape-rememorization ability would enhance the utility of elastic crystalline materials.Since diffusionless plastic deformability can preserve the crystallinity of materials,t he interconversion of diffusionless mechanical deformability between superelasticity and ferroelasticity could enable shape rememorization of superelastic single crystals.T his study demonstrates the shape rememorization of an organosuperelastic single crystal of 1,4-dicyanobenzene through time-reversible interconversion of superelasticity-ferroelasticity relaxation by holding the mechanically twinned crystal without heating. The shaperememorization ability of the organosuperelastic crystal indicates the compatibility of superelasticity (antiferroelasticity) and ferroelasticity as well as the intrinsic workability of organic crystalline materials capable of recovering their crystal functions under mild conditions. Practical applications of solid materials demand not only appropriate functions but also appropriate shapes.S ome polycrystalline and amorphous materials,s uch as alloys and polymers,are available in various shapes through molding in ad iffusion manner by thermal processes,i nw hich thermal stability is essential. On the other hand, reshaping singlecrystalline materials,i nw hich at hree-dimensional order is kept, is achieved by ac ombination of cutting,f iling, [1] and etching [2,3] according to their physical and chemical characteristics and intended use.R ecently,t he mechanical deformability of organic crystals has attracted great attention. Among their properties,s uperelasticity (SE) [18,[28][29][30][31] and ferroelasticity (FE) [19][20][21][22][23][24][25][26] give crystallographically well-regulated deformability while retaining single crystallinity. SE and FE have been developed in the fields of the materials science of metal alloys and the physics of ferroics, [32] respectively.M echanical deformations through both SE and FE are realized by diffusionless plastic deformability, whereby SE spontaneously recovers from strain and FE leaves permanent strain. In so-called shape-memory alloys (SMAs), [33][34][35] the shape is recovered because of the thermal generation of SE by as olid-state phase transition based on Gibbs free energy gaps,t hat is,m artensitic SE (mSE). Therefore,twinning deformation irrelevant to phase changes basically leads to twinning FE (tFE). Although tFE was claimed in an organic crystal of squaric acid in 1979, [19] tFE has now been identified in an increasing number of organic crystals and become commonplace in organic crystals composed of structurally flexible molecules. [19][20][21][22][23][24][25][26] Furthermore, multiple tFE effects with versatile deformability have been found in a1 ,4-diethoxybenzene crystal. [26] Tw inning deformability is apotential effective reshaping procedure for organic single crystals.Some organic crystals exhibit SE, so-called...

Experimental procedure and setup for obtaining X-ray fluorescence hologram of crystalline metalloprotein samples are described. Human hemoglobin, an α2β2 tetrameric metalloprotein containing the Fe(II) heme active-site in each chain, was chosen for this study because of its wealth of crystallographic data. A cold gas flow system was introduced to reduce X-ray radiation damage of protein crystals that are usually fragile and susceptible to damage. A χ-stage was installed to rotate the sample while avoiding intersection between the X-ray beam and the sample loop or holder, which is needed for supporting fragile protein crystals. Huge hemoglobin crystals (with a maximum size of 8 × 6 × 3 mm(3)) were prepared and used to keep the footprint of the incident X-ray beam smaller than the sample size during the entire course of the measurement with the incident angle of 0°-70°. Under these experimental and data acquisition conditions, we achieved the first observation of the X-ray fluorescence hologram pattern from the protein crystals with minimal radiation damage, opening up a new and potential method for investigating the stereochemistry of the metal active-sites in biomacromolecules.

No abstract

Hemoglobin, the vital O carrier in red blood cells, has long served as a classic example of an allosteric protein. Although high-resolution X-ray structural models are currently available for both the deoxy tense (T) and fully liganded relaxed (R) states of hemoglobin, much less is known about their dynamics, especially on the picosecond to subnanosecond time scales. Here, we investigate the picosecond dynamics of the deoxy and CO forms of human hemoglobin using quasielastic neutron scattering under near physiological conditions in order to extract the dynamics changes upon ligation. From the analysis of the global motions, we found that whereas the apparent diffusion coefficients of the deoxy form can be described by assuming translational and rotational diffusion of a rigid body, those of the CO form need to involve an additional contribution of internal large-scale motions. We also found that the local dynamics in the deoxy and CO forms are very similar in amplitude but are slightly lower in frequency in the former than in the latter. Our results reveal the presence of rapid large-scale motions in hemoglobin and further demonstrate that this internal mobility is governed allosterically by the ligation state of the heme group.

A newly identified microbial rhodopsin, NM-R3, from the marine flavobacterium Nonlabens marinus, was recently shown to drive chloride ion uptake, extending our understanding of the diversity of mechanisms for biological energy conversion. To clarify the mechanism underlying its function, we characterized the crystal structures of NM-R3 in both the dark state and early intermediate photoexcited states produced by laser pulses of different intensities and temperatures. The displacement of chloride ions at five different locations in the model reflected the detailed anion-conduction pathway, and the activity-related key residues—Cys105, Ser60, Gln224, and Phe90—were identified by mutation assays and spectroscopy. Comparisons with other proteins, including a closely related outward sodium ion pump, revealed key motifs and provided structural insights into light-driven ion transport across membranes by the NQ subfamily of rhodopsins. Unexpectedly, the response of the retinal in NM-R3 to photostimulation appears to be substantially different from that seen in bacteriorhodopsin.